Sunday will be the true first day of spring for interior decorators. This is when they will converge on Chelsea for the start of Europe’s biggest fabrics splash — London Design Week 2009. This fantastic free event, for trade (15-17 March) and the public (18-20 March), pulls in designers from all over the world and is centred around the big décor showrooms of Chelsea Harbour, and in nearby King’s Road.

Happily, the news is joyful and upbeat as decoration defies the downturn. New designs flaunt a feel-good factor that faces down the doom mongers. Flirty and floaty florals on smooth silks and soft linens will make you fall in love with your home all over again. “Well, we have to be extra pretty to beat the recession,” says designer Shauna Dennison at big brand Osborne & Little.

Butterflies and birds fly in charming patterns across fabrics, adding to the light touch of spring.

New “toiles” with simple, one-colour outlines of people and places suggest romantic stories. This favourite fabric genre dates back centuries, but now colours are strong and modern.

Metallics are no longer stiff and brash — their sheer threads have a subtle gleam and perfect drape, in varied tones of silver, bronze, copper and gold. Blocks of shimmering silver inks reflect the light — “these seem to have a patina,” says Dennison.

Embroidery is incredibly intricate, with shaded colours for a painterly effect on delicate voiles, with the back as neat as the front.

Damasks are still in favour, blurring hard baroque motifs. There is plenty of black-and-white (or cream/grey) but now softened with metallics. Adding weight are rich chenilles and velvets with deep piles cut into geometric patterns, inspired by everything from Art Deco to Africa.

Finer fibres add a new lustre

This season’s collections are so well co-ordinated that even a novice can combine patterns and mix in plains at the big fabric houses. Try Osborne & Little in the King’s Road, then pop across the street to Designers Guild, where spring collections pile on pattern without restraint — “romantic, irresistible, original and eccentric”, says their creator, Tricia Guild.

Chair in Pasha (£54 a metre) and cushion in Kara (£36 a metre), from Harlequin

As for colours, think pink and pink again. This girly hue is everywhere, from the palest of powder to the lush lipstick of cerise. Add aqua, sky and chartreuse, and mix in loads of lilac. Stronger shades are more grown-up — try chocolate, bronze and café-au-lait, topped with topaz, lime, or even purple.

And for neutrals, the trend is for deeper shades — “Subtle tones of white and greyed-off organic colours,” says Liz Cann of Zoffany, finger ever on the pulse. Sanderson’s new paint chart, for example, has ivory and creams, warmer tones of parchment and cooler architectural whites.

Curtains are served with all the trimmings, with choices way beyond the fringe. Now cut-crystal drop, faceted jet and glowing “jewels” drip at the edges of drapes. “Decorators who once would never touch a tassel love these contemporary effects,” says Jason d’Souza, who has his own brand.

From glitzy Hollywood to the tanned fish skins of Iceland

The most outre collection for spring comes from the work of Tony Duquette, legendary artist, interior decorator and Hollywood set designer, who died in 1999, at the age of 85.

His work — a marvellous melange of style, glamour and kitsch — ranged from sets and costumes for Fred Astaire musicals to grand (palatial even) interiors and furniture from all over the globe. Spinach Leopard — a vivid green skin pattern printed on to heavy linen, is only rivalled by Gemstone, a swirly green and black cotton that mimics the drama of malachite. Golden Sunburst is similarly splashy, on heavy silk. The firm of Jim Thompson, famous for fine Thai silks, is producing Duquette’s archive (www.jimthompson.com).

Similarly exotic, and a little defiantly from Iceland, is Arctic Designs, created by Ragna Erwin at Chelsea Harbour’s Chase Erwin fabric house. See fine-scaled fish “leather” in soft silvers, blues and a delicate purple. It comes from salmon caught in icy waters and tanned in a small Icelandic fishing village (www.arctic-designs.com).

What Londoners want

How do the main spring trends fit into Londoner’s lifestyles? Top interior designers tip us off — they’ll be giving talks and seminars throughout Design Week.

Doyen David Mlinarichas has spent more than 50 years in interior design. “We’re moving to a cosier, gentler look. It’s good news, because minimalism is expensive, both to achieve and to maintain. Now antique — or simply old — furniture, is cheap again. Buy it and mix it with modern because you really can have both.”

Farfalla butterfly wallpaper (£46 a roll) designed by Nina Campbell, available at Osborne & Little

Nicky Dobree does chic ski chalets and elegant London homes. “Home is now a haven: what is important is quality, comfort and sustainability. Small things can make a big difference. Even a lick of paint does wonders, with new cushions and throws. And recycle — say, re-upholster rather than buy new.

Kit Kemp is famous for her large collection of boutique hotels. She says “quality is the watchword, which means good design and doing things properly. Plan the job carefully and avoid expensive repeats.”

Joanne McEwan is design director of Montgomery, which does made-to-measure and ready-made curtains for specialists and for the big stores. Here are her new-season tips: